A mixture metering arrangement of this type is known, for example, from U.S. Pat. No. 4,442,817. In this patent, an arrangement is disclosed wherein the mixture composition is anticipatorily controlled in dependence on various operating parameters of the internal combustion engine and a superposed lambda control acts on these anticipatory control values in a corrective fashion. Because the internal combustion engine, as a controlled system, has a dead time which is primarily attributable to the time required for the gas to pass through the engine and to the response time of the lambda sensor, and because the lambda sensor output signal is nearly binary, a continuous oscillation occurs in the lambda control having a frequency which is determined by the dead time and an amplitude which is determined by the control parameters. The general rule here is that the higher the value of the control amplitude becomes, the faster disturbances are levelled.
On the other hand, with the control amplitude increasing, a rough operation of the internal combustion engine develops because of a torque change caused by the control. Further, particularly in situations of dynamic transition occurring during the operation of the internal combustion engine, undesirable exhaust peaks may occur as a result of excessive control oscillations. The reason for this is that in such an event the lambda control may temporarily run up against its limit. In the above-identified patent, it is suggested that the slope of the integral component of the control oscillation of the PI-controller be reduced to a minimum in successive correction cycles during steady or quasi-steady operational conditions of the internal combustion engine. If the internal combustion engine enters a steady operating condition, the slope of the integral component will be reduced to a predetermined maximum value. The process involved here is a pure control of the integrator slope which does not permit the compensation of long-term or short-term drifts occurring during the life of the internal combustion engine. In addition, this controlled adaptation of the integrator slope only takes effect during steady operating conditions.